Electric heater



April 29, 1952 P. LLOVFALD 2,594,465

ELECTRIC HEATER- Filed Jan. 25, 1949 IN V EN TOR.

Patented Apr. 29, 1952 UNITED STATES PATENT OFFICE ELECTRIC HEATER PeerLovfald, Lincrcft, N. J.

Application January 25, 1949, Serial No. 72,679

1 Claim. 1

This invention relates to improvements in electric heaters andparticularly it refers to an electric heater having low surfacetemperature and having so-called explosion-proof construction for use inoil refineries or other places where explosive or ignitible gases ormaterials are present.

Most present electric heaters suffer from a common defect in that theirsurface temperatures are too high. Even those which have totallyenclosed elements often have surface temperatures way above the flashpoint of most volatile solvents such as acetone, benzene, naphtha, etc.,as well as those of any number of combustible gas mixtures. It has,therefore, not been possible to use electric heaters in many placeswhere such heaters otherwise would be highly desirable. In oilrefineries, for instance, many heating installations are required whereelectric heating is the only practical solution. Due to the fact thatthe surface temperatures were too high, it was not always possible toinstall such heaters and yet obtain the highest standards of safety. Myinvention eliminates this difficulty and furnishes a heater with a lowsurface temperature which is safe for all such installations as abovementioned.

An important object of my invention is to provide an electric heaterwith low surface tem perature and with explosion-proof fittings.

A further object of my invention is to provide an electric heater withinan explosion-proof metal housing of low cost and simple constructionthat will give long, safe and trouble free service.

Other objects and advantages of my invention will be apparent during thecourse of the following description.

In the accompanying drawing, forming a part of this specification, andin which like numerals designate like parts throughout the same,

Figure 1 is a side elevation in perspective of an electric heaterembodying my invention,

Figure 2 is a longitudinal section taken along the center line, and,

Figure 3 is a transverse section taken along line 3-3 in Figure 2.

In the drawing, wherein for the purpose of illustration, is shown apreferred embodiment of my invention, the numeral 5 designates theheating element proper which is preferably of hairpin shape, as shown,and consists of a suitable resistance wire sealed in an outer steeltubing with a flexible insulating material capable of withstanding thetemperature of the wire. The hairpinshaped heating element 5 terminatesin the leadin wires 6 which are brazed to the wires of the insulatedcable 1 which goes through the explosion-proof fittings 8 and 9 to theconduit ID.

The hairpin-shaped heating element 5 is cast into a metal tube II withmetal fins 12. A disc of insulating material l3 closes one end of tubeH. In a preferred embodiment the tube Il may be of steel with copperfins l2 while the metal [4 which is cast around the element 5 isaluminum which has a suitable melting point. The tube l l is supportedat one end by the elbow l5 and rod is which has a flange l1 forfastening to the floor or wall. The other end of tube H is threaded intothe reducer l8 which is connected to the fitting 8 by means of nippleIS.

A suitable housing of perforated or expanded metal is mounted over thefinished heater as designated by numeral 26 in Figure 1. The sealingcondulet or fitting 9 is filled with a suitable sealing compound whichprevents any gas vapor or explosive mixture from entering the fittingsurrounding the terminal connections. The fittings 8 and 9 are ofsufficient strength to withstand an explosion on the outside withoutadmitting any explosive gases, and sufficiently tight to prevent anysparks or flame to escape from inside the fittings and thereby igniteany combustibles outside same.

The operation of my invention is similar to that of any other electricheater. The differonce is to be found in the fact that due to the methodof casting the hairpin element 5 in the metal [4 in tube H the radiatingsurface becomes very much greater. This is further enhanced by the metalfins 12 which act to cool the tube H and thereby still further reducingthe surface temperature of same to a point where complete safety isachieved.

It is to be understood that the form of my invention, herewith shown anddescribed, is to be taken as a preferred example of same, and thatvarious changes in the shape, size, metals and materials used andarrangement of parts may be resorted to, without departing from thespirit of my invention, or the scope of the subjoined claim.

Having thus described my invention, I claim:

A low temperature explosionproof electric heater of the characterdescribed comprising, a finned tubular body threaded at both ends, ahairpinshaped electric heating element cast in aluminum into said finnedtubular body, a mounting elbow placed on one end of said body, a threadreducer placed on the other end of said body where the leads from saidheating element come out, and an explosionproof fitting threaded intosaid reducer.

PEER LOVFALD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,472,171 Haynsworth Oct. 30,1923 1,591,141 Phillips July 6, 1926 2,317,426 Wilson Apr. 27, 19432,450,921 Smith Oct. 12, 1948 2,473,783 Brown, Jr June 21, 1949

